1. Field of the Invention
The present invention relates to a resin container which accommodates liquid.
2. Description of the Related Art
When liquid such as an industrial drug is accommodated in a resin container which is integrally molded into a drum shape by blow molding so as to be stored or conveyed, a pipe is used for discharging the liquid in some cases. Conventionally, as illustrated in FIG. 5A, a pipe 150 of which one end is attached to an outlet port 125 provided on a ceiling plate 120 of a resin container 100 is lowered straightly toward a bottom plate 110 so that liquid is discharged. A method of discharging the liquid is classified broadly into a method of connecting a pump to the pipe to suck the liquid (hereinafter, referred to as “suction system”) and a method of feeding the air into the container and pressurizing the liquid to push out the liquid through the pipe (hereinafter, referred to as “pressure feeding system”).
Irregularities are formed on the bottom plate of the resin container which is integrally molded normally. Therefore, in the conventional resin container, there has been a problem that liquid present on a portion of a recessed surface, which is separated from a position of a lower end of the pipe due to a protruding portion, is not discharged and is left. A height of the irregularities on the bottom plate of a common resin container is not so high. However, as a capacity of the container is increased, an area of the bottom plate is increased so that a volume of residual liquid is also increased. For example, in the conventional resin container having a capacity of 200 liters, a residual liquid amount when the liquid is discharged with the suction system is as large as equal to or larger than 1.5 liters.
Further, when the liquid is discharged with the pressure feeding system, as illustrated in FIG. 5B, the bottom plate 120 expands outward with increase of a pressure in the resin container 100 so that the lower end of the pipe 150 is distanced from the bottom plate 110. In addition, the ceiling plate 120 also expands outward and the outlet port 125 is inclined. With this, the pipe 150 is inclined so that the lower end of the pipe 150 is largely distanced from the bottom plate 110 further. Therefore, in the case of the pressure feeding system, the liquid cannot be discharged at a time when the liquid level becomes lower than the lower end of the pipe 150 with the discharge of the liquid. Therefore, the residual liquid amount is large. For example, in the conventional resin container having a capacity of 200 liters, the residual liquid amount when the liquid is discharged with the pressure feeding system is as large as approximately 5 liters.
The liquid which has not been discharged from the resin container and has been left is to be discarded and is wasteful as resource. Further, there are a number of extremely expensive liquids among the industrial drugs. Therefore, a technique of reducing a residual liquid amount has been desired in terms of reduction in cost.